Later work saw him develop glass-reinforced plastic as an alternative to steel and concrete in bridges, a move that enhanced his reputation as an innovator.
He was also noted for emphasising the aesthetic importance of engineering. His Institution of Structural Engineers presidential address was filled with references to the architect Le Corbusier and philosopher Immanuel Kant.
After suffering a stroke in 1994, Lee retired from his directorship at Maunsell, which he joined in 1955.